Continuous rolling system

1. A continuous rolling system that changes product specifications during continuous rolling of one strip of a material to be rolled, comprising:

a tandem rolling mill including a plurality of rolling stands, each of the plurality of rolling stands controlling a roll gap according to a roll gap operation value;

a strip thickness gauge provided on a delivery side of the tandem rolling mill, the strip thickness gage measuring strip thickness of the material to be rolled; and

a roll force distribution control device matching an actual roll force ratio between the plurality of rolling stands with a target roll force ratio;

wherein

the roll force distribution control device comprising:

a setting calculation unit determining:

a strip thickness target value of each of the plurality of rolling stands; and

a roll force distribution ratio target value of each of the plurality of rolling stands, the roll force distribution ratio target value representing the target roll force ratio between the plurality of rolling stands;

an actual data collection unit collecting:

a roll force actual value of each of the plurality of rolling stands;

a roll gap actual value of each of the plurality of stands, the roll gap actual value being calculated based on the roll gap operation value of each of the plurality of rolling stands;

a roll rotational speed actual value of each of the plurality of rolling stands; and

a strip thickness measurement value obtained by measurement with the strip thickness gauge;

a mass flow thickness correction unit performing:

calculating a strip thickness actual value of each of the plurality of rolling stands based on the strip thickness measurement value and the roll rotational speed actual value of each of the plurality of rolling stands;

calculating a strip thickness actual recalculation value of each of the plurality of rolling stands based on the roll force actual value of each of the plurality of rolling stands and the roll gap actual value of each of the plurality of rolling stands;

calculating a gap error of each of the plurality of rolling stands based on a difference between the strip thickness actual value of each of the plurality of rolling stands and the strip thickness actual recalculation value of each of the plurality of rolling stands; and

calculating a gap correction value of each of the plurality of rolling stands, the gap correction value being for preventing the gap error of each of the plurality of rolling stands from being changed;

a target strip thickness correction value calculation unit performing:

calculating a roll force distribution ratio actual value of each of the plurality of rolling stands, the roll force distribution ratio actual value representing the actual roll force ratio between the plurality of rolling stands, based on the roll force actual value of each of the plurality of rolling stands; and

calculating a target strip thickness correction value of each of the plurality of stands based on a difference between the roll force distribution ratio target value of each of the plurality of rolling stands and the roll force distribution ratio actual value of each of the plurality of rolling stands;

a tracking unit tracking a tracking point, the tracking point being set on the material to be rolled; and

a gap operation unit outputting the roll gap operation value to a target rolling stand when the tracking point reaches each of the plurality of rolling stands, wherein

the rolling stand to which the tracking point reaches is set as the target rolling stand,

the roll gap operation value is calculated to bring a difference between a first value and a second value to zero,

the first value being obtained by correcting the strip thickness target value of the target rolling stand with the target strip thickness correction value of the target rolling stand, and

the second value being obtained by correcting the strip thickness actual recalculation value of the target rolling stand with the gap correction value of the target rolling stand.

2. The continuous rolling system according to claim 1 , wherein

the gap correction value is a correction value bringing to zero a difference between a correction reference gap error and a non-head-end gap error, the correction reference gap error being the gap error when a head end of the material to be rolled reaches the rolling stand, the non-head-end gap error being the gap error when a part other than the head end of the material to be rolled reaches the rolling stand.

3. The continuous rolling system according to claim 2 , wherein

the roll force distribution control device performs:

interrupting calculation of the gap correction value and the target strip thickness correction value before executing a flying strip thickness change, the flying strip thickness change causing the strip thickness target value of the tandem rolling mill to be changed without stopping rolling by the tandem rolling mill;

storing the correction reference gap error before execution of the flying strip thickness change;

resetting the roll force distribution ratio target value for the flying strip thickness change;

calculating the correction reference gap error after the execution of the flying strip thickness change, by adding a difference to the correction reference gap error before the execution of the flying strip thickness change, the difference being between the gap error after the execution of the flying strip thickness change and the gap error before the execution of the flying strip thickness change; and

resuming the calculation of the gap correction value and the target strip thickness correction value after calculating the correction reference gap error after the execution of the flying strip thickness change.

4. The continuous rolling system according to claim 3 , wherein

the roll force distribution control device reduces the gap error gradually with time, the gap error occurring during changing of strip thickness by the flying strip thickness change.

5. The continuous rolling system according to claim 1 , comprising:

a gap operation end intervention unit allowing the roll gap operation value to be changed based on an intervention signal by an operator;

wherein

the roll force distribution control device performs:

calculating the roll force distribution ratio actual value of each of the plurality of rolling stands based on the roll force actual value of each of the plurality of rolling stands, the roll force actual value being collected after the roll gap operation value having been changed is applied to the tandem rolling mill; and

updating the roll force distribution ratio target value of each of the plurality of rolling stands with the roll force distribution ratio actual value of each of the plurality of rolling stands.

6. The continuous rolling system according to claim 1 , wherein

the roll force distribution control device performs:

storing a table defining a relationship between a type and size of the material to be rolled and a control gain; and

obtaining, from the table, the control gain corresponding to the type and size of the material to be rolled; and

the gap correction value is calculated by multiplication by the control gain; and

the target strip thickness correction value is calculated by multiplication by the control gain.

7. The continuous rolling system according to claim 1 , wherein

the rolling stand includes an actuator controlling a shape of the material to be rolled; and

the roll force distribution control device performs change of the roll force distribution ratio target value of the rolling stand having the actuator, the change being performed in a direction of reducing an output of the actuator when the output reaches an upper limit value and in a direction of increasing an output of the actuator when the output reaches a lower limit value.

8. A continuous rolling system that changes product specifications during continuous rolling of one strip of a material to be rolled, comprising:

a tandem rolling mill including a plurality of rolling stands, each of the plurality of rolling stands controlling a roll gap according to a roll gap operation value;

a strip thickness gauge provided on a delivery side of the tandem rolling mill, the strip thickness gage measuring strip thickness of the material to be rolled; and

a roll force distribution control device matching an actual roll force ratio between the plurality of rolling stands with a target roll force ratio;

wherein

the roll force distribution control device comprising:

circuitry configured to

determine a strip thickness target value of each of the plurality of rolling stands, and a roll force distribution ratio target value of each of the plurality of rolling stands, the roll force distribution ratio target value representing the target roll force ratio between the plurality of rolling stands,

collect a roll force actual value of each of the plurality of rolling stands, a roll gap actual value of each of the plurality of stands, a roll rotational speed actual value of each of the plurality of rolling stands, and a strip thickness measurement value obtained by measurement with the strip thickness gauge, the roll gap actual value being calculated based on the roll gap operation value of each of the plurality of rolling stands,

calculate a strip thickness actual value of each of the plurality of rolling stands based on the strip thickness measurement value and the roll rotational speed actual value of each of the plurality of rolling stands,

calculate a strip thickness actual recalculation value of each of the plurality of rolling stands based on the roll force actual value of each of the plurality of rolling stands and the roll gap actual value of each of the plurality of rolling stands,

calculate a gap error of each of the plurality of rolling stands based on a difference between the strip thickness actual value of each of the plurality of rolling stands and the strip thickness actual recalculation value of each of the plurality of rolling stands,

calculate a gap correction value of each of the plurality of rolling stands, the gap correction value being for preventing the gap error of each of the plurality of rolling stands from being changed,

calculate a roll force distribution ratio actual value of each of the plurality of rolling stands, the roll force distribution ratio actual value representing the actual roll force ratio between the plurality of rolling stands, based on the roll force actual value of each of the plurality of rolling stands,

calculate a target strip thickness correction value of each of the plurality of stands based on a difference between the roll force distribution ratio target value of each of the plurality of rolling stands and the roll force distribution ratio actual value of each of the plurality of rolling stands,

track a tracking point, the tracking point being set on the material to be rolled, and

output the roll gap operation value to a target rolling stand when the tracking point reaches each of the plurality of rolling stands, wherein

the rolling stand to which the tracking point reaches is set as the target rolling stand,

the roll gap operation value is calculated to bring a difference between a first value and a second value to zero,

the first value being obtained by correcting the strip thickness target value of the target rolling stand with the target strip thickness correction value of the target rolling stand, and

the second value being obtained by correcting the strip thickness actual recalculation value of the target rolling stand with the gap correction value of the target rolling stand.

9. The continuous rolling system according to claim 8 , wherein

the gap correction value is a correction value bringing to zero a difference between a correction reference gap error and a non-head-end gap error, the correction reference gap error being the gap error when a head end of the material to be rolled reaches the rolling stand, the non-head-end gap error being the gap error when a part other than the head end of the material to be rolled reaches the rolling stand.

10. The continuous rolling system according to claim 9 , wherein

the circuitry is further configured to

interrupt calculation of the gap correction value and the target strip thickness correction value before executing a flying strip thickness change, the flying strip thickness change causing the strip thickness target value of the tandem rolling mill to be changed without stopping rolling by the tandem rolling mill,

store the correction reference gap error before execution of the flying strip thickness change,

reset the roll force distribution ratio target value for the flying strip thickness change,

calculate the correction reference gap error after the execution of the flying strip thickness change, by adding a difference to the correction reference gap error before the execution of the flying strip thickness change, the difference being between the gap error after the execution of the flying strip thickness change and the gap error before the execution of the flying strip thickness change, and

resume the calculation of the gap correction value and the target strip thickness correction value after calculating the correction reference gap error after the execution of the flying strip thickness change.

11. The continuous rolling system according to claim 10 , wherein

the circuitry reduces the gap error gradually with time, the gap error occurring during changing of strip thickness by the flying strip thickness change.

12. The continuous rolling system according to claim 1 , wherein

the circuitry is further configured to

allow the roll gap operation value to be changed based on an intervention signal by an operator,

calculate the roll force distribution ratio actual value of each of the plurality of rolling stands based on the roll force actual value of each of the plurality of rolling stands, the roll force actual value being collected after the roll gap operation value having been changed is applied to the tandem rolling mill, and

update the roll force distribution ratio target value of each of the plurality of rolling stands with the roll force distribution ratio actual value of each of the plurality of rolling stands.

13. The continuous rolling system according to claim 8 , wherein

the circuitry is further configured to

store a table defining a relationship between a type and size of the material to be rolled and a control gain, and

obtain, from the table, the control gain corresponding to the type and size of the material to be rolled, and

the gap correction value is calculated by multiplication by the control gain; and

the target strip thickness correction value is calculated by multiplication by the control gain.

14. The continuous rolling system according to claim 8 , wherein

the rolling stand includes an actuator controlling a shape of the material to be rolled; and

the circuitry performs change of the roll force distribution ratio target value of the rolling stand having the actuator, the change being performed in a direction of reducing an output of the actuator when the output reaches an upper limit value and in a direction of increasing an output of the actuator when the output reaches a lower limit value.

15. A roll force distribution control device comprising:

circuitry configured to

determine a strip thickness target value of each of a plurality of rolling stands of a tandem rolling mill, and a roll force distribution ratio target value of each of the plurality of rolling stands, each of the plurality of rolling stands controlling a roll gap according to a roll gap operation value, the roll force distribution ratio target value representing a target roll force ratio between the plurality of rolling stands,

collect a roll force actual value of each of the plurality of rolling stands, a roll gap actual value of each of the plurality of stands, a roll rotational speed actual value of each of the plurality of rolling stands, and a strip thickness measurement value obtained by measurement with a strip thickness gauge, the strip thickness gauge being provided on a delivery side of the tandem rolling mill and measuring strip thickness of a material to be rolled, the roll gap actual value being calculated based on the roll gap operation value of each of the plurality of rolling stands,

calculate a strip thickness actual value of each of the plurality of rolling stands based on the strip thickness measurement value and the roll rotational speed actual value of each of the plurality of rolling stands,

calculate a strip thickness actual recalculation value of each of the plurality of rolling stands based on the roll force actual value of each of the plurality of rolling stands and the roll gap actual value of each of the plurality of rolling stands,

calculate a gap error of each of the plurality of rolling stands based on a difference between the strip thickness actual value of each of the plurality of rolling stands and the strip thickness actual recalculation value of each of the plurality of rolling stands,

calculate a gap correction value of each of the plurality of rolling stands, the gap correction value being for preventing the gap error of each of the plurality of rolling stands from being changed,

calculate a roll force distribution ratio actual value of each of the plurality of rolling stands, the roll force distribution ratio actual value representing an actual roll force ratio between the plurality of rolling stands, based on the roll force actual value of each of the plurality of rolling stands,

calculate a target strip thickness correction value of each of the plurality of stands based on a difference between the roll force distribution ratio target value of each of the plurality of rolling stands and the roll force distribution ratio actual value of each of the plurality of rolling stands,

track a tracking point, the tracking point being set on the material to be rolled, and

output the roll gap operation value to a target rolling stand when the tracking point reaches each of the plurality of rolling stands, wherein

the rolling stand to which the tracking point reaches is set as the target rolling stand,

the roll gap operation value is calculated to bring a difference between a first value and a second value to zero,

the first value being obtained by correcting the strip thickness target value of the target rolling stand with the target strip thickness correction value of the target rolling stand, and

the second value being obtained by correcting the strip thickness actual recalculation value of the target rolling stand with the gap correction value of the target rolling stand.